Detection system for control information

ABSTRACT

Disclosed herein is a detection system for control information transmitted from the sending side to the receiving side in a broadcast system, in which the control information is detected in consideration of the following two conditions: (1) if a control signal representative of the control information is intermitted by the control at the sending side or by noise, the control signal is deemed continuous in case of the intermitted time of the control signal is less than a predetermined first time (t); and (2) if a signal deemed continuous exceeds a predetermined second time (T) longer than the first time (t), this signal is decided as the control information.

United States Patent Fukata [151 3,657,655 [4 1 Apr. 18, 1972 DETECTION SYSTEM FOR CONTROL INFORMATION Primary ExaminerRobert L. Griffin Assistant Examiner-Kenneth W. Weinstein [72] Inventor: Masayuki Fukata 94 Shimorenjaku, b D

Mitakashi, y p Attorney R0 ert M unnmg [22] Filed: Apr. 15, 1969 [57] ABSTRACT [-21 A N 816,295 Disclosed herein is a detection system for control information transmitted from the sending side to the receiving side in a broadcast system, in which the control information is detected [:2] Cl 325/364 3 in consideration of the following two conditions: (1) if a con- 5 [1/16 trol signal representative of the control information is interg -MC 343/228 mitted by the control at the sending side or by noise, the con- [58] [e o earc trol signal is deemed continuous in case of the intermitted 56 R f d time of the control signalis less than a predetermined first 1 e erences n time (t); and (2) if a signal deemed continuous exceeds a UNITED STATES PATENTS predetermined second time (T) longer than the first time (t),

this signal is decided as the control information. 3,513,399 5/1970 Wycoff ..325/466 3,496,467 2/ 1970 Lundgreen ..325/64 X 5 Claims, 12 Drawing Figures 2 3 4 5 mi RECEIVER FREQU HEY-{E Mi. DR 2078 t I RERAY r l CIRCUIT OR'VER 1 INVERTER 9 EEE l AMA/7150i PULE I ,0 z WI T SELECTOR W255 TIMER "47 I I4 i PAIENTEMR 181912 3.557, 655 SHEET 10F 6 INVENTOR.

MA5A Vu/(A Fu/m TA PATENTEDAPR 18 m2 3, 657, 655 sum 2 6F 6 Law 1-? CE I VER AMPLITUDE SELECTOR Fig. 4 75 IN VEN TOR.

MAS/l YUK/ Fz/m TA PATENTEDAPR 18 1912 3, 657, 655

SHEET k 0F 6 LOW l3 RECEIVER msggaycvfi L RELAY L CIRCUIT If l2 FILTER INVERTER DRIVER w r I f "Mr M4? /0 RECTI- AMPLITUDE PULSE BIS TABLE FIER ksmcran I lsfi'x'afi m cmcum TIMER set 12 4 i--r-i P1%i-1 ur 14 Set I F1 9 8 I I INT/ENTORR MAS/I YUK FU/{ATA PATENTEUAPR 18 m2 3, 657, 655

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DETECTION SYSTEM FOR CONTROL INFORMATION This invention relates to a detection system of control information transmitted from the sending side to the receiving side in a broadcast system, particularly in l an emergency broadcast system for transmitting emergency information, such as information of a natural disaster etc., from the broadcast station to the receivers, (2) a recorder-control broadcast system for causing recorders of the receivers, such as tape-recorders, to record the broadcast information in accordance with the control of the broadcast station, or (3) a broadcast system for a control signal transmitted to control the switch operation of each of various kinds of apparatus at the receiving side.

In the conventional system of the type (e.g., the emergency broadcast system), the emergency control signal is sent out from the sending side, such as the broadcast station, before the broadcast of emergency information. In this case, if a broadcast program is being sent out, the emergency control signal is sent out together with the broadcast program. However, if the broadcast program is interrupted, only the emer gency control signal is sent out. The emergency control signal is generally a continuous or intermittent wave or waves each having a predetermined frequency, or it may be a frequencywobbled wave or waves in consideration of discordance among frequency-characteristics of respective receivingselection circuits at the receivers. If there are many kinds of the emergency control signals to be transmitted, a plurality of signal-waves are employed instead of a single wave. Amplitude-modulation or frequency-modulation may be employed as the modulation system of this case. The emergency information will be set out after sending the above-mentioned emergency control signal.

On the other hand, the receiver side each providing with a receiving set, such as a radio receiving set or a television set, is established in the stand-by condition for receiving the emergency control signal. In other words, the video pattern and/or the audio output of the receiving set are/is not seen or heard because of the inactive state of the video circuit and/or the audio circuit. The receiving set is designed so that if an emergency control signal is transmitted from the sending side, the receiving-and-selection circuit of the emergency control signal provided at the receiver side receives and selects only the transmitted emergency control signal and then actuates the video circuit and/or the audio circuit. Accordingly, if a predetermined emergency control signal is received at a receiver, the video circuit and/or the audio circuit of the receiver is switched from the inactive state to the active state in which the emergency information following after the emergency control signal can be received at the receiver in the receiver's eyes and/or ears.

In this system, it is essential that in consideration of the nature of the emergency information, the emergency information to be transmitted is reliably transmitted to each of the receivers in 100 percent efficiency and, in a case of no transmission of the emergency control signal, the receiving-andselection circuit does not at all carry out the spurious triggering in which it detects in error a like signal as the emergency control signal (hereinafter called a false signal) as the regular emergency control signal.

In conventional broadcast systems of control information, detection systems of the control information mentioned below are employed.

1. System A A continuous signal of a single frequency is used as the control information, and the detecting means decides as regular control information when the duration of the continuous signal exceeds a predetermined time.

2. System B An intermittent signal of a single frequency is used as the control information, and the detecting means decides as regular information when the number of intermitted parts of the intermittent signal exceeds a predetermined number.

4. System D Each of the continuous signals used in the System B is so modified as mentioned in System C.

However, the abovementioned conventional systems have the following defects. Broadcast signals are apt to be affected by noise since they are usually transmitted in the air. In Systems A and B, a part of the continuous signal is ready to eliminated by the noise so that the transmitted control information cannot be correctly detected due to the storage of the duration of the continuous signal. This will cause NON- TRIGGERING at the receiving side. Moreover, the number of intermitted parts is ready to be incorrectly counted in the systems C and D so that a false signal is detected as the regular control information. This will cause SPURIOUS-TRIG- GERING at the receiving side. If the intermitted spaces are filled up with noise, the transmitted information will not be detected (NON-TRIGGERING).

Therefore, an object of this invention is to provide a detection system of control information transmitted in broadcast system, in which the abovementioned defects of conventional systems is eliminatable and the control information is detected without error.

In the detection system of this invention, the control infor mation is detected in consideration of the following two conditions.

Condition 1 If a control signal is intermitted by the control at the sending side or by noises, the control signal is deemed continuous in case of the intermitted time of the control signal does not exceed a predetermined time (2).

Condition II If a signal deemed continuous exceeds a predetermined time (T), this signal is decided as the regular control signal.

Accordingly, since the duration of the control signal is not measured in accordance with actual intermitted parts thereof, the decision of the control infonnation is performable without error even if a part or parts of the control signal is/are affected by noise. Moreover, since the number of intermitted parts of the control signal is not counted while the abovementioned conventional system counts the number, detection of the con trol information is carried out without error even iffalse parts are inserted in the control signal due to noise.

The principle of this invention will be better understood from the following more detailed discussion taken in conjunction with the accompanying drawings, in which the same or equivalent parts are designated by the same reference numerals, characters and symbols, and in which:

FIGS. 1 and 2 show time charts for describing the principle of this invention;

FIGS. 3, 5 and 7 are block diagrams for illustrating embodi ments of this invention applied at the receiving side of a broadcast system;

FIGS. 4, 6 and 8 are time charts for describing the operations of the block diagrams shown in FIGS. 3, 4 and 7 respectively;

FIG. 9 is a block diagram for illustrating embodiments of this. invention applied at the sending side and the receiving side in a broadcast system;

FIG. 10 shows characteristic curves for describing the frequency characteristics of filters used in detectors of this invention in the embodiment shown in FIG. 10;

FIG. 11 is a block diagram for illustrating an embodiment of this invention to detect the control information comprising a A combination of a plurality of continuous signals having plurality of t n s; and

FIG. 12 shows time charts for describing the operation of the embodiment shown in FIG. 11.

The principle of this invention will be at first described concretely with reference to time charts. Waves w,, w, and W shown in FIG. 1 are examples of signals having a single frequency. These signals are deemed equivalent to a continuoussignal w, in view of the condition I since any of intermitted times of these signals is less than a time (2) determined so as to be shorter than the time length of the control signal. Moreover, the signal W4 is detected as a control signal in view of the condition II since the duration of this signal w, exceeds a time (T) determined so as to be more than the time length of the control signal. Waves w, and w shown in FIG. 2 are other examples of signals having a single frequency. However, since each of these signals w, and w has an interrnitted space longer than the time (1), so that these signals W5 and w, are deemed equivalent to an intermitted signal w Accordingly, any of these signals W and w is not detected as a control signal since the duration of continuous part in each of the signals w and w is less than the time (T).

With reference to FIG. 3, an example of receiving means used to detect control information in accordance with this invention is an emergency broadcast system will be described. It

is assumed as a matter of convenience that the receiving means is designed to receive a voice information and that the control information is of a tone of a single frequency (fl amplitude modulated by a rectangular wave. In this example, a receiver 2 receives a transmitted wave through an antenna 1 and demodulates it to a voice signal similarly as an ordinary radio receiver. A filter 6 selects a signal (e.g.; w in FIG. 4) of the frequency f from the voice signal. A rectifier 7 rectifies the signal w and cuts off the frequency )1, from the rectified output to produce a pulse signal W12. An amplitude selector 8 selects and amplifies parts of the signal W12 exceeding a predetermined level. A pulse width expander 9 expands the duration of each of its input pulses by a time (t) from the termination thereof as shown by a'wave W This pulse width expander 8 can be formed by use of a mono-stable circuit using transistors. A wave w is an example of the output signal of the pulse width expander 9 for the pulse signal W A timer 10 continues and stops the time measurement when the signal of an input 1 assumes mark polarity and space polarity respectively. The timer resets the result of the time measurement to its original state when the signal of an input I (an output of an inverter 11) assumes mark polarity. If the duration of the signal of the input I, exceeds the time (T), the timer 10 generates an output pulse signal. A wave w is an example of the charged voltage in the timer 10 in case where the timer 10 is designed by use of the charging time of a capacitor. In this example, when the charged voltage (w exceeds a predetermined threshold voltage V a pulse signal w is generated from the timer 10. This pulse w drives, through a driver 12, a relay circuit 13 having self-holding function. If the relay circuit 13 is turned to its ON-state" as shown by a wave W18, a switch 3 is also switched to ON-state. In this case, the voice signal from the receiver 2 is sounded from a speaker through a low frequency amplifier 4.

The timer may be designed by use of a digital counter. The relay circuit 13 may be fonned by use of a mechanical relay or transistors etc. Moreover, the switch 3 may be used to ON-OFF control of the power of the low frequency amplifier 4. The detector DR illustrated in FIG. 3 may be applied to control a television receiver or a facsimile receiver. The selfholding function of the relay circuit 13 can be restored by the succeeding control signal transmitted from the sending side.

FIG. 5 shows a modification of the example shown in FIG. 3. In this example, the input I, of the timer 10 is applied from the output of the amplitude selector 8. Accordingly, the time measurement of the timer 10 interrupts as shown by a voltage w in FIG. 6 at space polarity of the input I Since the operation of the example can be easily understood with reference to FIG. 6 and the operation of the example shown in FIG. 3, details are omitted.

The example shown in FIG. 5 may be formed as shown in FIG. 7. In this example shown in FIG. 7, a bistable circuit 14 is used so as to be set by mark polarity of the input I (e.g.; w and to be reset by mark polarity" of the input I (e.g.; w The timer l0 continues the time measurement when the bistable circuit 14 is set to the state l and restores the result of the time measurement when bistable circuit 14 is reset to the state 0; The operation of this example will be understood with reference to time charts shown in FIG. 8.

The above-mentioned examples can detect control signals of other types. For example, even if a control signal having a predetermined duration (e.g.; T) of continuous part is used, this control signal will be detected in accordance with this invention without error.

As mentioned above, the control information signal can be detected without error even if the control information signal is affected by noise in the transmission path. While the control information is transmitted in, before or after a broadcast program, there is a fair chance for including a fore-mentioned false signal in the broadcast information. FIG. 9 shows a broadcast system of the control information eliminatable of the chance of the false signal. In this system, a detector DR having one of the above-mentioned types with reference to FIGS 3, 5 and 7 is provided at the receiving side. Moreover, a detector DT similar to the detector DR is provided at the sending side as disclosed in my U.S. application for patent (Ser. No. 701,031). This detector DT is so designed that this detects the false signal before the spurious triggering of any of the receiving sets by the false signal. Ifthe detector DT detects a false signal, a control circuit 28 controls switches 22 and 23 so as to insert, in the path of the broadcast program applied from a terminal 20, a band elimination filter 24 to eliminate the same frequency component as the frequency (f of the control signal applied from the terminal 21. The insertion time of the band elimination filter 24 is determined at an appropriate time longer than the time (t). It is desirable that the band elimination filter 24 eliminates lower harmonic components f,/2, f,/3, f,,/4, of the frequency (fi,) to eliminate completely the possibility of conversion of the lower components f /2, f,/3, f,/4 to their higher harmonic frequency (f,) at the transmission path including a transmitter 26 and the receiver 2.

To meet the above mentioned requirements, it is essential that the detector DT is designed under the following conditions:

a. The time determined under the condition II is longer than the time (T).

b. The band width F, of the filter 6 is determined in consideration of discordance of the frequency characteristics F F F of the filters 6 of all the receiving sets so as to cover all the frequency characteristics F F F as shown in FIG. 10.

c. The clipping level of the amplitude selector 8 is determined so as to be lower than that of any of the receiving sets.

d. The extension time of the pulse width expander 9 is determined so as to be longer than that (t) of any of the receiving sets.

If the control information is formed by a plurality of tones, each of the detectors DR and DT is formed as shown in FIG. 11. In this example, an AND circuit 15 produces a logical product of a plurality of tones. Time charts shown in FIG. 12 are wave forms of respective parts designeated in FIG. 11. This example is based on the type of the detector shown in FIG. 3. However, the detector DR or DT for the control information of a plurality of tones may be also designed on the base of the examples shown in FIGS. 5 and 7.

What I claim is:

1. A system for detecting control information transmitted in a transmission path of a broadcast system, comprising:

selection means coupled with the transmission path for selecting at least one frequency representative of the control information,

rectifying means connected to the output of said selection means for rectifying the output signal of the selection means so as to produce pulses of periods equal to the periods of respective continuous signals from the output of said selection means,

a pulse-width expander connected to the rectifying means for expanding, by a first time (t), the duration of each of said pulses so as to produce a continuous DC voltage when the intermitted periods in the control information signals are less than said first time (t), and decision means connected to the output of the pulse-width expander for deciding when the duration of the continuous DC voltage exceeds a predetermined second time (T) and for producing an indication thereof.

2. A detection system of control information according to claim 1, in which the decision means comprises a timer performing the time measurement by the output of the pulse width expander and restoring .the measurement result thereof by the inverse signal of the output of the pulse width expander.

3. A detection system of control information according to claim 1, in which the decision means comprises a timer performing the time measurement by the output rectified of the selection meansand restoring the measurement result thereof by the inverse signal of the output of the pulse width expander.

4. A detection system of control information according to claim 1, in which the decision means comprises a bistable circuit set by the output rectified of the selection means and reset by the inverse signal of the output of the pulse width expander, and a timer performing the time measurement in a case of the set state of the bistable circuit and restoring the measurement result thereof in a case of the reset state of the bistable circuit.

5. A detection system of control information according to claim 1, in which a plurality of selection means is provided for selecting a plurality of tones representative of the control in formation, and a logical product of the outputs of the selection means is applied to the pulse width expander. 

1. A system for detecting control information transmitted in a transmission path of a broadcast system, comprising: selection means coupled with the transmission path for selecting at least one frequency representative of the control information, rectifying means connected to the output of said selection means for rectifying the output signal of the selection means so as to produce pulses of periods equal to the periods of respective continuous signals from the output of said selection means, a pulse-width expander connected to the rectifying means for expanding, by a first time (t), the duration of each of said pulses so as to produce a continuous DC voltage when the intermitted periods in the control information signals are less than said first time (t), and decision means connected to the output of the pulse-width expander for deciding when the duration of the continuous DC voltage exceeds a predetermined second time (T) and for producing an indication thereof.
 2. A detection system of control information according to claim 1, in which the decision means comprises a timer performing the time measurement by the output of the pulse width expander and restoring the measurement result thereof by the inverse signal of the output of the pulse width expander.
 3. A detection system of control information according to claim 1, in which the decision means comprises a timer performing the time measurement by the output rectified of the selection means and restoring the measurement result thereof by the inverse signal of the output of the pulse width expander.
 4. A detection system of control information according to claim 1, in which the decision means comprises a bistable circuit set by the output rectified of the selection means and reset by the inverse signal of the output of the pulse width expander, and a timer performing the time measurement in a case of the set state of the bistable circuit and restoring the measurement result thereof in a case of the reset state of the bistable circuit.
 5. A detection system of control information according to claim 1, in which a plurality of selectiOn means is provided for selecting a plurality of tones representative of the control information, and a logical product of the outputs of the selection means is applied to the pulse width expander. 